"After a lot of thought I have decided not to appeal the fine NASCAR has issued," Hamlin tweeted Thursday. "Dragging myself, my team and NASCAR through the mud for the next 2 weeks would not be good for anyone.

"I firmly believe I am in the right on this issue and will stand behind my decision not to pay. I understand NASCAR will do what they feel is necessary based on my decision. Thanks to all of my fans and peers who have supported me in this decision. I look forward to putting it to rest."

NASCAR announced Thursday that Hamlin had dropped the appeal and that the case was settled.

"The $25,000 fine assessed to driver Denny Hamlin on March 7 will be settled per Section 12-3 of the 2013 NASCAR rule book after being informed by Hamlin that he will not appeal the penalty," NASCAR said in a statement. " … NASCAR considers this matter closed."

According to its rules, NASCAR could suspend Hamlin for not paying the fine or deduct the fine from his race winnings. Since it announced that the case is closed and did not announce a suspension, it apparently plans to deduct the fine from Hamlin's winnings.

NASCAR debuted its Gen-6 car this year. Hamlin said after the Phoenix race that the car did not race as well yet as the old model.

"I don't want to be the pessimist, but it did not race as good as our generation five cars," Hamlin said after finishing third at Phoenix. "This is more like what the generation five was at the beginning. The teams hadn't figured out how to get the aero balance right.

"Right now, you just run single-file and you cannot get around the guy in front of you. You would have placed me in 20th-place with 30 (laps) to go, I would have stayed there."

NASCAR fined Hamlin for "actions detrimental to stock-car racing" for what NASCAR officials said were "disparaging remarks."

NASCAR officials said it would not tolerate comments by drivers that "denigrate the racing product."

Hamlin was livid over the penalty and vowed to fight it.

"I don't believe in this," he said shortly after being informed about the fine. "I'm never going to believe in it. So as far as I'm concerned, I'm not going to pay the fine.

"If they suspend me, they suspend me. I don't care at this point."

Hamlin, whose stance was supported by many fans and some other drivers, said he did not understand the penalty.

"The bad part of it is I feel like I've been a pretty good spokesman for them in being positive when things aren't always positive," Hamlin said.

"They just lost one small spokesman today. That's all."

Team owner Joe Gibbs said last week that Joe Gibbs Racing supported Hamlin's decision to appeal the penalty.